The present invention relates generally to a device for winding threads.
More particularly, it relates to a device for winding threads which has a spool spindle, a guide roll and a changing unit with two oppositely driven rotors having at least two propeller-like wings.
Devices of the above mentioned general type are known in the art. Wing changing devices are suitable especially for the use with high changing frequencies. In contrast to the conventional changing devices, the alternative movement of the thread is performed not by a single reciprocating thread guide, but instead by oppositely rotating wings which alternatingly engage and guide the threads. Since the wings at the end points of the changing region neither accelerate nor retarded the influence of the carrier mass of the thread guiding element during the thread reverse is completely eliminated.
The oppositely moving wings of both rotors meet at predetermined fixed meeting points. The meeting points are distributed with uniform angular distances over a rotary circle. The angular distances depend on the number of wings of a rotor. When a rotor has for example two wings, it amounts to 90 degree. The changing takes place between two neighboring meeting points. The wing which is located correspondingly in the region of this quarter circular arc leads the thread. When it reaches the meeting point, it is transmitted to the oppositely coming wing of the other rotor. After this angle of exactly 90 degree is covered, the thread is taken up by the second wing of the first rotor, etc. For a disturbance free winding and an unobjectionable spool formation, especially at the end surfaces, an exact thread transfer to the end points of the changing region is important.
In known spooling machines the both rotors of the wing changing device are offset relative to one another so that the axis of one rotor is displaced in direction of the changing stroke, or in other words parallel to the coil axis. Thereby the transfer of the thread from one wing of one rotor to the oppositely coming wing of the other rotor is facilitated. At both meeting points which mark the end points of the changing region, the corresponding receiving wing extends outwardly beyond the rotary circle of the transmitting wing. The preceding wing end takes the thread which is transmitted from the wing tip of the transmitting wing, as disclosed in the German document DE-OS 33 07 915.
The European patent document EP-A1-0 322 752 discloses a spooling machine in which two rotors are arranged coaxially relative to one another. Additional guiding elements are provided for exact thread transfer at the ends of the changing region.
In the known spooling machines the changing device is arranged with multiple inclinations, so that between the rotary planes of the wings and an incoming thread an acute angle is provided. Due to the inclined position, the thread length between the changing wings and the guiding rollers arranged behind them can be retained very small. This feature is important for an exact thread guidance. Due to the inclined position the rotary circle of the wing which rotates in the rotary plane spaced further from the guiding roller, extends a little beyond the rotary circle of the wing of the other roller. At the end point of the changing region, at which one of the first mentioned wings takes the thread, this wing is in contact with the thread a little bit too early. At the other end it transfers the thread a little bit too late.
These disturbing effect can be counteracted by forming and arranging the guiding arm differently at both reversing points. This is however expensive and difficult to reproduce. Also, during optimal adjustment it has been observed that at both end surfaces of the coil a different coil formation is produced because of the different constellation of the wings and a different movement course during the thread transfer.